'''
In this exercise, you'll be simulating the movement of objects through 2D space, 
such as a bouncing ball as well as random diffusion.

The code below simulates a ball moving from the left to the right side of the 
graphical window:
'''

xSize = 800 
ySize = 600 
ballx = 1 
bally = 300 
dx = 1.0 
nsteps = 1000 
 
c = color().green 

screen = canvas("title", xSize, ySize) 
pen = writer(screen) 
 
for i in range(nsteps): 
    ballx = ballx + dx 
    pen.drawCircle(ballx, bally, 5, c, True) 
    screen.update() 
    screen.pause(5) 
    screen.clear() 

screen.keepwindow() 

'''
Exercise A:
Run the code above and observe the result. 
Then increase and decrease the speed at which the ball moves by modifying the 
value for `dx`.

Exercise B:
Extend the code such that the ball initially moves very fast, then gradually 
slows down before finally stopping at the right border of the graphical window, 
by making `dx` depend on the position of the ball within the graphical window. 

Exercise C:
Extend the code such that the ball moves from top to bottom. Add a variable 
named `dy`.

Exercise D:
Extend the code such that the ball moves in a diagonal line over the graphical 
window. 

'''